[MacCatalyst] Stop soft-linking UIKit in WebProcessCocoa.mm

https://bugs.webkit.org/show_bug.cgi?id=271890
<rdar://125613749>

Reviewed by Per Arne Vollan.

* Source/WebKit/Platform/spi/ios/UIKitSPI.h:
- Import the appropriate header for internal SDK builds, and declare the
  method for public SDK builds.
* Source/WebKit/WebProcess/cocoa/WebProcessCocoa.mm:
(WebKit::WebProcess::platformInitializeWebProcess):
- Remove soft-linking and availability check since this method is always
  available since at least macOS 11.3.

Canonical link: https://commits.webkit.org/276832@main

Source/WebKit/Platform/spi/ios/UIKitSPI.h

@@ -31,6 +31,7 @@
 #import <UIKit/NSTextAlternatives.h>
 #import <UIKit/UIActivityViewController_Private.h>
 #import <UIKit/UIAlertController_Private.h>
+#import <UIKit/UIApplication+iOSMac_Private.h>
 #import <UIKit/UIApplication_Private.h>
 #import <UIKit/UIBarButtonItem_Private.h>
 #import <UIKit/UIBlurEffect_Private.h>
@@ -1014,6 +1015,10 @@ extern NSNotificationName const _UIWindowSceneDidEndLiveResizeNotification;
 
 #endif // HAVE(UI_WINDOW_SCENE_LIVE_RESIZE)
 
+#if HAVE(CATALYST_USER_INTERFACE_IDIOM_AND_SCALE_FACTOR)
+extern void _UIApplicationCatalystRequestViewServiceIdiomAndScaleFactor(UIUserInterfaceIdiom, CGFloat scaleFactor);
+#endif
+
 #endif // USE(APPLE_INTERNAL_SDK)
 
 #if ENABLE(OVERLAY_REGIONS_IN_EVENT_REGION)

Source/WebKit/WebProcess/cocoa/WebProcessCocoa.mm

@@ -185,12 +185,6 @@
 #import <pal/cocoa/DataDetectorsCoreSoftLink.h>
 #import <pal/cocoa/MediaToolboxSoftLink.h>
 
-#if HAVE(CATALYST_USER_INTERFACE_IDIOM_AND_SCALE_FACTOR)
-// FIXME: This is only for binary compatibility with versions of UIKit in macOS 11 that are missing the change in <rdar://problem/68524148>.
-SOFT_LINK_FRAMEWORK(UIKit)
-SOFT_LINK_FUNCTION_MAY_FAIL_FOR_SOURCE(WebKit, UIKit, _UIApplicationCatalystRequestViewServiceIdiomAndScaleFactor, void, (UIUserInterfaceIdiom idiom, CGFloat scaleFactor), (idiom, scaleFactor))
-#endif
-
 #define RELEASE_LOG_SESSION_ID (m_sessionID ? m_sessionID->toUInt64() : 0)
 #define WEBPROCESS_RELEASE_LOG(channel, fmt, ...) RELEASE_LOG(channel, "%p - [sessionID=%" PRIu64 "] WebProcess::" fmt, this, RELEASE_LOG_SESSION_ID, ##__VA_ARGS__)
 #define WEBPROCESS_RELEASE_LOG_ERROR(channel, fmt, ...) RELEASE_LOG_ERROR(channel, "%p - [sessionID=%" PRIu64 "] WebProcess::" fmt, this, RELEASE_LOG_SESSION_ID, ##__VA_ARGS__)
@@ -348,12 +342,10 @@ static void setVideoDecoderBehaviors(OptionSet<VideoDecoderBehavior> videoDecode
     applyProcessCreationParameters(parameters.auxiliaryProcessParameters);
 
     setQOS(parameters.latencyQOS, parameters.throughputQOS);
-    
+
 #if HAVE(CATALYST_USER_INTERFACE_IDIOM_AND_SCALE_FACTOR)
-    if (canLoad_UIKit__UIApplicationCatalystRequestViewServiceIdiomAndScaleFactor()) {
-        auto [overrideUserInterfaceIdiom, overrideScaleFactor] = parameters.overrideUserInterfaceIdiomAndScale;
-        softLink_UIKit__UIApplicationCatalystRequestViewServiceIdiomAndScaleFactor(static_cast<UIUserInterfaceIdiom>(overrideUserInterfaceIdiom), overrideScaleFactor);
-    }
+    auto [overrideUserInterfaceIdiom, overrideScaleFactor] = parameters.overrideUserInterfaceIdiomAndScale;
+    _UIApplicationCatalystRequestViewServiceIdiomAndScaleFactor(static_cast<UIUserInterfaceIdiom>(overrideUserInterfaceIdiom), overrideScaleFactor);
 #endif
 
     populateMobileGestaltCache(WTFMove(parameters.mobileGestaltExtensionHandle));